https://www.repository.cam.ac.uk/bitstream/1810/264501/1/Fu_et_al-2017-Progress_in_Material_Science-VoR.pdf

Advances in piezoelectric thin films for acoustic biosensors, acoustofluidics and lab-on-chip applications

https://iopscience.iop.org/article/10.1088/0964-1726/25/5/053002/pdf

Piezoelectric thin films: an integrated review of transducers and energy harvesting

An integrated volatile organic toxicants sensor with a Bluetooth device interface has been developed. The device is based on novel tuning fork sensor platform along with a wireless communication/interface technology taken in an integrated system approach. It features high sensitivity and selectivity. The sensitivity and selectivity are accomplished through the use of novel tuning fork sensor modified by design (molecularly imprinted) polymers and selective filtering. Experiments have shown that the device can detect toxic volatile organic compounds (VOCs) under high concentrations of common interferents from flavors and fragrances. Applications of the device for detection of BTEX in real-world situations such as outdoor and gas station VOCs have also been demonstrated. All these features make the device a promising candidate to be deployed in real-world applications, particularly in environmental health and air pollution studies.

A Wearable and Wireless Sensor System for Real-Time Monitoring of Toxic Environmental Volatile Organic Compounds

This paper is a review of the remarkable progress that has been made during the past few decades in design, modeling, and fabrication of micromachined resonators. Although micro-resonators have come a long way since their early days of development, they are yet to fulfill the rightful vision of their pervasive use across a wide variety of applications. This is partially due to the complexities associated with the physics that limit their performance, the intricacies involved in the processes that are used in their manufacturing, and the trade-offs in using different transduction mechanisms for their implementation. This work is intended to offer a brief introduction to all such details with references to the most influential contributions in the field for those interested in a deeper understanding of the material.

Micromachined Resonators: A Review

This paper discusses piezoelectric acoustic devices based on widely used piezoelectric materials. Commonly used piezoelectric thin film deposition techniques and the influence of process parameters on the growth, texture and orientation of the films are discussed. Etching techniques are also outlined. A comparative study of different devices developed previously is given. Also, applications of developed devices in aero-acoustic and medical fields have been briefly discussed. Flow charts of various techniques of deposition along with a combined one for full acoustic device fabrication are given. Various techniques, frequently used for thin film characterization have been discussed. The testing and measurement techniques to determine the responses of acoustic devices such as sensitivity, resonance frequency, frequency response, piezoelectric co-efficient etc. have been briefly illustrated. This paper discusses common failure modes with respect to the field of use of acoustic devices. It also concisely discusses various reliability tests done in industries to assess the quality of the developed devices. This review has also suggested directions for future development of thin film acoustic sensors.

Piezoelectric MEMS based acoustic sensors: A review

Film bulk acoustic resonators (FBAR) have recently been adopted as alternatives to surface acoustic wave (SAW) in high frequency devices, due to their inherent advantages, such as low insertion loss, high power handling capability and small size. FBAR device can also be one of the standard components as mass sensor applications. FBAR sensors have high sensitivity, good linearity, low hysteresis and wide adaptability. In this study, a highly sensitive mass sensor using film bulk acoustic resonator was developed. The device structure of FBAR is simulated and designed by the Mason model, and fabricated using micro electromechanical systems (MEMS) processes. The fabricated FBAR sensor exhibits a resonant frequency of 2442.188 MHz, measured using an HP8720 network analyzer and a CASCADE probe station. Experimental results indicate that the mass loading effects agree with the simulated ones. Results of this study demonstrate that the sensitivity of the device can be achieved as high as 3654 Hz cm2/ng.

Highly sensitive mass sensor using film bulk acoustic resonator

This study investigates high-performance ZnO piezoelectric films used for thin film bulk acoustic resonators (TFBAR). The ZnO piezoelectric film was deposited on a Pt/Ti electrode using an RF magnetron sputter by a two-step method at room temperature. The Pt/Ti electrode was deposited by a DC sputtering system, on which, ZnO piezoelectric films were deposited in one step and in two steps to minimize roughness in the first step and produce the preferred orientation in the second. Both field-emission scanning electron microscopy (FESEM) and atom force microscopy (AFM) revealed that ZnO piezoelectric film deposited by two-step sputtering exhibited favorable characteristics, such as a rigidly precise surface structure with surface roughness of 7.37 nm, even better than in one-step sputtering. Examining the ZnO thin film by X-ray diffraction (XRD) showed a much higher c-axis-preferring orientation than in one-step sputtering. The reflection coefficient of the resonator device was measured using an HP8720 network analyzer. The frequency response of the FBAR device exhibited a return loss of -25 dB at a resonant frequency of 2212 MHz with a high coupling coefficient of 6.7%.

Lin Re-Ching

Papers

Highly sensitive mass sensor using film bulk acoustic resonator

Two-step sputtered ZnO piezoelectric films for film bulk acoustic resonators

Wind-power generators based on ZnO piezoelectric thin films on stainless steel substrates

Deposition and structural properties of RF magnetron-sputtered ZnO thin films on Pt/Ti/SiNx/Si substrate for FBAR device

Design and fabrication of a piezoelectric transducer for wind-power generator